ENGR 100 Lecture Notes - Lecture 28: Diffraction Grating, Miller Index, Diffraction
Document Summary
Polymorphism when a metal or nonmetal has more then one crystal structure. Allotropy the conditions referred to when polymorphism is found in a elemental solid. There are seven different crystal systems, we probably only need to know the two already discussed, cubic and hexagonal. \ The position of any point located within a unit cell may be specified in terms of its coordinates as fractional multiples of the unit cell edge lengths. Planes a represented in a similar manner to the crystallographic directions. In all except the hexagonal crystal system the planes are specified by three. Directional equivalency is related to linear density in a sense that for a particular material, equivalent directions have identical linear densities. A similar parameter applies to crystallographic planes, planar density. Corresponding planes having the same planar density values are also equivalent. Planar density takes as the number of atoms per unit area that are centered on a particular crystallographic plane.
